Method of preventing scaling during the forging of hollow metal articles



March 1943- w. MARENCIK METHOD OF PREVENTING SCALING DURING THE FORGINGOF HULLOW METAL ARTICLES Filed Aug. 25,. 1944 a .i w

1 M W B Patented 2, 1948 METHOD OF PREVENTING SCALING DUR- ING THEFORGING OF HOLLOW METAL ARTICLES William J. Marencik, Pal-ma, Ohio,assignor to Thompson Products, Inc., Cleveland, Ohio, a

corporation of Ohio Application August 25, 1944, Serial No. 551,195

This invention relates to a method of P ing scaling during the forgingof hollow metal articles, and more particularly to-a method ofpreventing the scaling of the internal surface of a cup-shaped metalblank in forging the same into a hollow head valve.

In making hollow head poppet valves for aircraft or other automotiveengines, a cup-shaped metal blank is subjected to a series of hotforging operations to form an elongated solid stem portion and a headportion provided with a cavity therein. One such method is described andclaimed. in the McBride et al, Patent No. 1,984,751. During the hotforging operations, which are carried out at a sufficiently elevatedtemperature to cause scale formation, scale forms on the internalsurface of the cup-shaped blank and remains on such surface after theforgingoperations are complete. It has heretofore been a very difficultand expensive task to remove this scale in finishing the hollow headvalve for the reception of a coolant, such as metallic sodium. Thisscale must, however, be completely removed to prevent contamination ofthe coolant with the scale and also to obtain an eflicient rate of heattransfer through the metal of the valve to the coolant contained withinthe hollow head thereof.

I have now found that the surface of a hollow metal article can besatisfactorily protected from scaling and oxidation during the hotforging thereof from blank forms if the internal surface of the blankitself is sealed against the entrance thereinto of air and hot gasesduring the forging steps. In accordance with my present invention, thisis accomplished by applying a metal cap to the open end of the blank anddeforming the metal of the blank to secure the cap in place thereon. Thecap is so applied and secured in place while the blank is cool and theinternal surface thereof entirely free from scale or oxides. Since thecap then remains in place during the subsequent hot forging operations,or other form of heat treatment, the internal surface of the blank hasno opportunity to become oxidized, other than through the action of thesmall amount of air sealed within the blank at the start. to beobjectionable, but if it should prove to be so, the air in the blankcavity can first be displaced by means of carbondioxide. or other inertgas. Carbondioxide is preferred because being heavier than air, it willdisplace air if introduced into the blank either in gaseous form, or inthe form of solid carbon-dioxide.

As a further protection for the internal sur- This amount of oxidationis not sufilcient 5 Claims. (01. 29-15) faces of the blank during thehot forging operations, the capped end of the blank may be coated withglass-forming ingredients, such as frit, as disclosed in the copendingapplication of myself and Robert E. Ahlf, Serial No. 551,194, filedAugust 25, 1944. Ordinarily, however, if the metal cap is properlysecured in place on the open end of the cup-shaped blank, as by peeningover the metal of the blank, a gas-tight seal is thereby provided thatprevents the occurrence of scale formation on the internal surface ofthe blank during the hot forging operations; The metal cap remains inplace during the forging or other operations and becomes included in themetal of the blank. Prior to the forming of the finished hollow metalarticle, the portion of the forged blank that includes the metal of thecap is removed. The internal surface of the article has now beenprevented from becomin scaled during all of the operations performed inmaking the finished article that involve scaling temperatures.

It is therefore an important object of this invention to provide amethod of preventing-the formation of scale and oxides on the internalsurfaces of metal articles during the hot forging of the blanks in theproduction of such articles.

It is a further important object of this invention to provide a methodof preventing scale formation during the hot forging of metal blanks inthe manufacture of hollow metal articles, such as hollow head valves andthe like, wherein the interior of the blank is sealed by a metal capwhile the internal surface thereof is free from scale or oxides, the capremaining in place during the subsequent hot forging operations to sealthe interior of the blank and protect the internal surface thereof untilafter all operations at elevated temperatures have been completed,

Other and further important objects of this invention will be apparentfrom the disclosures in the, specification and the accompanyingdrawing.

0n the drawings:

Figure 1 is a longitudinal sectional view of a cup-shaped blank with ametal can applied to the open end thereof and with a peening hammer inposition before striking the end of the blank to peen the metal of theblank about the periphery of the metal cap.

Figure 2 is a view similar to Figure l with the peening hammer in theact of performing the peening operation.

Figure 3 is a longitudinal sectional view of a icup-shaped blank withthe cap secured in posiion.

Figure 4 is a longitudinal sectional view of the valve blank in onestage of its manufacture after being subjected to a hot forging step.

Figure 5 is a longitudinal sectional view of the valve blank after beingsubjected to a further hot forging step that results in closing-the stemend of the valve blank.

Figure 6 is a longitudinal sectional view, similar to Figure 3,illustrating the application of a further protective coating over thecapped end of the blank.

Although the invention here illustrated and described is applied to themanufacture of hollow head valves, such as aircraft valves, it will beunderstood that it is similarly applicable to the manufacture of anyhollow metal article which is formed from a cup-shaped blank by a seriesof hot forging operations. In the case of a hollow head valve, these hotforging operations include the use of hammers to reduce the diameter ofthe blank adjacent its head end and thereby form a neck portion, andalso the use of extrusion dies, swedging dies, upsetting dies, and thelike. During such hot forging operations, temperatures are used, such asin the neighborhood of about 1,800 to 2,100" F., that would normallycause scale formation on the surfaces of the metal blank. Since theseoperations are of themselves well known and some of them are describedin the McBride et al patent above referred to, they will not beexplained in detail here.

The reference numeral it indicates generally a cup-shaped blank such asis used in the forming of a hollow head valve. The blank I is itself theresult of a series of prior operations and comprises an enlarged headportion II and a stem portion l2 of slightly reduced diameter. Withinthe head portion II is a head cavity l3 which merges into a stem cavityll. Prior to the start of the operations about to be described. thevalve blank ID has been machined to leave the internal surface of thehead and stem cavities l3 and I4, respectively, clean and free from anyscale or oxides.

With the valve blank It in the cleaned condition indicated, the open endof the blank is sealed before the blank is subjected to any hightemperatures in the course of manufacturing the hollow head valve.

As illustrated in Figures 1 and 2, the open stem end of the blank Ill isrecessed, as at [5, to receive a metal cap I6 to provide a seal for theinterior of the blank. Said metal blank i6, which may be formed ofstainless steel or other suitable metal, is preferably initially dishedto give it a convexity upwardly as illustrated in Figure 1. The metalcap it is placed in the annular recess l and then struck with a peeninghammer II. The bottom face of said hammer I1 is provided with asegmental spherical concave surface I8 centrally and with a surroundingconical recess it. The action of the hammer I1 is thus to give asegmental spherical contour to the metal cap l6 and to cause the metalof the end of the blank to fiow over and around the periphery of themetal cap l6, as at 20. The cap "5 is thereby firmly sealed in place andthe internal walls of the blank III are sealed against the entrance ofair or gases thereinto.

Starting with the capped blank III as illustrated in Figure 3, the blankis subjected to a series of hot forging operations as a result of whichthe blank passes through the stages illustrated in Figures 4 and 5. Inone of the hot forging operations, the blank I0 is reduced to provide aneck 2| and an elongated stem portion 22, also of reduced diameter. Themetal cap ll during this forging step becomes deformed and assumes aslightly angular shape. The shape is of no particular importance exceptthat it indicates the behavior of the metal cap when the blank issubjected to the forging operations to form the neck and stem of reduceddiameter. when a stainless steel cap is used, no diillculty isexperienced from the cap breaking or rupturing.

In a second forging operation, the valve blank I0 is subjected to anextrusion step that results in closing the stem of the valve to providean elongated closed stem 23 and a head cavity 24.

The metal of the cap l6, now indicated by the reference numeral Ilia, isenclosed within the metal of the elongated stem 22. Since the mass ofthe cap metal 16a is substantially at the extremity of the stem portion,the stem end can be severed, as at the dotted line 26 (Figure 5) toeliminate the cap metal entirely from the finished valve. Subsequentoperations beyond those illustrated are carried out to produce thefinished valve, but since these operations do not involve temperaturesat which scaling would take place, no further protection of the surfaceof the head cavity 24 is required. The elongated stem 23 is drilled outto permit the introduction of a coolant, such as metallic sodium, intothe head cavity 24, and the valve blank otherwise finished in accordancewith well known practice.

In the modification of my invention illustrated in Figure 6, in additionto a metal cap it. the end' of the valve blank l0, including said capI6, is provided with a coating of material, such as frit, capable uponfusing of forming a glassy protective layer 26. To accomplish this, anaqueous suspension of frit is applied to the end of the valve blank ID,as by dipping or spraying, to form a layer 26 thereover. After the endof the blank has been coated with a layer of the aqueous fritsuspension, it is subjected to a preliminary heating step, as by heatingto about 200 F. to dry the frit coating to form a dry, relatively hardadherent layer 26. During the subsequent hot forging operations, thislayer 26 becomes fused to form a glassy protective coating over theentire end of the blank, thus insuring complete protection of theinterior wall of the valve blank during the hot forging operations. Asbefore stated, the cap continues to protect the interior as the valvetakes shape, because it does not resist deformation but collapses uponitself without breaking the seal. The glassy coating 26, however,protects against the possibility of the metal cap i6 drawing away fromthe peened over metal bead 20 to produce a leak in the seal.

In accordance with the principles of this invention, therefore, hollowmetal articles may be protected against surface oxidation or scaling bythe use of either a thin metal cap alone or a metal cap and a protectiveglassy coating to seal the blank cavity during hot forging operations.

I claim as my invention:

1. In the method of making a hollow head valve in which a cup-shapedblank is subjected to a series of hot forging operations, theimprovement whereby scaling of the internal surface of the blank isprevented, which comprises applying an outwardly dished metal cap to theopen end of said blank to seal the empty cavity therein, peening themetal of said blank about said cap to secure the same in place and sealthe interior of said blank, and subsequently subjecting said blank tohot forging operations.

5 a 2. In the method of making a hollowhead valve in which a cup-shapedblank is subjected to a series of hot forsinz operations, theimprovement whereby scaling of the internal surface of the blank isprevented which comprises applying an outwardly dished metal cap to theopen end of said blank to seal the empty cavity therein, peening themetal of said blank about said cap to secure the same in place and sealthe interior of said blank prior to subjecting said blank to hot forgingoperations, hot forging said blank to form a hollow head, a reduced neckand an elongated solid stem with the metal of said cap included in theend of said stem and removing said stem end that includes the metal ofsaid cap.

3. In the method of making a hollow head valve in which a cup-shapedblank is subjected to a series of hot forging operations, theimprovement whereby scaling of the internal surface of the blank-isprevented, which comprises applying an outwardly dished metal cap to theopen end of said blank, peening the metal of said blank about said capto secure the same in place and seal the empty interior of said blankprior to subjecting said blank to hot forging operation, hot forgingsaid blank to form a hollow head, a reduced neck and an elongated solidstem with the metal of said cap included in the end of said stem andremoving said stem end.

4. In the method of making a hollow head valve from a cup-shaped blankby a series of hot forging operations, the improvement preventingscaling of the internal surface of said blank,

which comprises applying an outwardly dished metal cap to the open endof said blank while securing said cap in place by deformation of themetal of said blank to seal the empty interior thereof, subjecting saidblank to hot forging operations during which the metal of said capbecomes included within the metal of said blank, and thereafter removingthe portion of the blank that includes said cap metal.

5. In the method of making a hollow head valve from a cup-shaped blankby a series of hot forging operations, the improvement'preventingscaling of the internal surface of said blank, which comprises applyingan outwardly dished metal cap to theopen end of said blank to seal theempty cavity therein while the internal surface is clean and free fromscale, securing said cap in place by deformation of the metal of saidblank, applying a frit coating over said cap to protect the cap end ofsaid blank and to seal the interior thereof, subjecting said sealedblank to hot forging operations during which the metal of said capbecomes included within the metal of said blank, and thereafter removingthe portion of the blank that includes said cap metal.

WILLIAM J. MARENCIK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,364,565 Lloyd Jan. 4, 19211,409,562 Mason Mar. 14, 1922 2,005,306 Wallis June 18, 193E 2,081,645Squires May 25, 193'. 2,093,771 Colwell Sept. 21, 193'.

